The main objective of the application is simulation and testing of a practical, high-resolution, three-dimensional (3-D) mammographic x-ray system in vitro. The process makes use of a new tomosynthetic reconstruction scheme called tuned-aperture computed tomography (TACT). This method is based on an extension of optical aperture theory that links conventional transmission radiography with computed tomography. It differs fundamentally from other tomographic methods by virtue of that fact that all projection information required for 3-D reconstruction is derived from two-dimensional (2-D) projections whose projection geometry is unknown at the time of exposure. This difference facilitates the production of high-resolution 3-D imager over extended periods of time using relatively simple technology derived from existing mammography units. The research plan involves reconfiguring a conventional solid-state mammography system based on an existing digital detector to simulate TACT, undertaking comprehensive analyses using specially-developed test objects to compare imaging performance in 3-D with theoretical predictions, and using resulting information as a guide for simulating clinical performance in vitro. Through these simulations TACT is to be compared clinically with conventional mammographic images for diagnostic performance obtainable from specially selected and prepared cadaveric specimens using ROC analysis for lesion-detection tasks and appropriate parametric analyses for lesion-location tasks.